"""

"""

__author__ = 'jing'


class A:
    def __getitem__(self, item):
        if item > 3:
            raise IndexError
        return item


class B(A):
    def __iter__(self):
        yield 'a'
        yield 'b'
        yield 'c'


for i in A():
    pr(i)
for i in B():
    pr(i)
